Bring to full, bubbling boil over medium-high heat, stirring constantly with wooden spoon, about 3 minutes. Stir down bubbles, then remove from heat. Stir in remaining vanilla. Whisk eggs in mixing bowl. While continuing to whisk, add a few tablespoons hot syrup to eggs, then whisk eggs into hot syrup, beating well as you do so (strain mixture if lumpy).

Pour hot filling into partially baked pastry shell and arrange nuts on top. Bake about 30 minutes, or until knife inserted in center comes out clean or coated with clear syrup.